I'm not sure the THM200 was out in '75 but it definitely was by '77 The General did use them by then also available were the as you thought THM350 and the same one with less clutch pack discs [less drag and the "Powerhouse" engine was 125HP so no need for the whole enchilada for that] the THM250, There is supposed to be a way to tell from the outside but I don't remember what that "Tell" was/is for the 250->350 They are the same case apparently That was a long time ago best check with a knowledgeable "Tranny" guy if you have one and don't know for sure. Harry Ok I had to check I was somewhat close: https://en.wikipedia.org/wiki/Turbo-Hydramatic and https://www.youtube.com/watch?v=khIAYGy1c20

I'm not a hoarder I'm a preservationist 78 Monza Spyder (Soon To Be 2+2 with Spoilers)

I answered my own question an hour ago. Based on GM's list of transmission specs, my 75's have the TH350 and my 76 has the TH200. Got curious because I yarded the engine and trans out of the 76 and was looking at the trans last night. Having never seen a TH200 before, was sort of surprised that it doesn't have a removable tail shaft housing like a TH350 or TH400. Since I am building one of my 75's with a 4 speed and one with an auto, I wanted to have at least a TH350 in it. Didn't have a way to peak under the 75's right now since sitting in the dirt is just too low, lol. Sort of odd though, could not find any Monza related specs that said anything other than " 3 speed turbo hydromatic with torque converter".

Some people are like slinkies. They serve absolutely no useful purpose, but still put a smile on your face when pushed down a flight of stairs.